Modelling prior distributions of atoms for macromolecular refinement and completion
Acta Crystallographica Section D
Volume 56, Issue 10, pages 1316–1323, October 2000
How to Cite
Roversi, P., Blanc, E., Vonrhein, C., Evans, G. and Bricogne, G. (2000), Modelling prior distributions of atoms for macromolecular refinement and completion. Acta Crystallographica Section D, 56: 1316–1323. doi: 10.1107/S0907444900008490
- homographic exponential models;
- macromolecular refinement;
- probability distributions.
Until modelling is complete, macromolecular structures are refined in the absence of a model for some of the atoms in the crystal. Techniques for defining positional probability distributions of atoms, and using them to model the missing part of a macromolecular crystal structure and the bulk solvent, are described. The starting information may consist of either a tentative structural model for the missing atoms or an electron-density map. During structure completion and refinement, the use of probability distributions enables the retention of low-resolution phase information while avoiding premature commitment to uncertain higher resolution features. Homographic exponential modelling is proposed as a flexible, compact and robust parametrization that proves to be superior to a traditional Fourier expansion in approximating a model protein envelope. The homographic exponential model also has potential applications to ab initio phasing of Fourier amplitudes associated with macromolecular envelopes.